The subtitle for this excellent book is ‘Climategate and the corruption of science’ which sums up the sad tale. Montford succeeds in making a technical statistical argument quite readable, which is surely a sign of divine assistance.

In brief, and cutting out much fascinating detail, the story is this:
– until the mid-1990’s the consensus on climate history was that there was a ‘Medieval Warm Period’ (with temperatures higher than today), followed by a ‘Little Ice Age’, and then, from about 1850, a rise in temperature through to today;
– in the late 1990’s a group led by Michael Mann devised a new history in which those highs and lows were flattened out, and the rise in temperature in the twentieth century was emphasised – this is the ‘hockey stick’;
– the scientific rationale for the hockey stick was progressively investigated, especially by Steven McIntyre, and has been comprehensively demolished;
– the scientific credibility of the IPCC in this regard is less than zero;
– the ‘hockey team’ – ie those around Mann and supporting his work – resorted to a great many dirty tricks and obfuscations to confuse this truth. “Climategate” was simply the airing of the dirty laundry (almost certainly a leak from somebody inside who was disgusted by the attempt at covering up the truth).

The funny thing is that the hockey stick as such is pretty marginal to the question of whether AGW is true or not. It can, however, serve as something of a litmus test – anyone who accepts it reveals that they are ill-informed. For me, this is the most significant chart re AGW:

Even if we do nothing (and we won’t, so this is worst case) the CO2 concentration is likely to peak at around 450ppm, roughly equal to a .7C rise in temperature.